| Number | 338
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| Category | errata
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| Synopsis | Syntax 14-4, A.7.4: syntax of edge sensitive module path descriptions
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| State | lrmdraft
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| Class | errata-simple
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| Arrival-Date | Apr 29 2003
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| Originator | Dennis Marsa <drm@xilinx.com>
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| Release | 2001b: Syntax 14-4, A.7.4
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| Environment |
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| Description |
In 1364-1995, the syntax for edge sensitive module path descriptions is described by the following BNF rules in A.7, and in syntax box 13-5. parallel_edge_sensitive_path_description ::= "(" [ edge_identifier ] specify_input_terminal_descriptor "=>" specify_output_terminal_descriptor [ polarity_operator ] ":" data_source_expression ")" ")" full_edge_sensitive_path_description ::= "(" [ edge_identifier ] list_of_path_inputs "*>" list_of_path_outputs [ polarity_operator ] ":" data_source_expression ")" ")" In 1364-2001, the syntax for edge sensitive module path descriptions was changed to the following (in A.7.4, and in syntax box 14-4): parallel_edge_sensitive_path_description ::= "(" [ edge_identifier ] specify_input_terminal_descriptor "=>" specify_output_terminal_descriptor [ polarity_operator ] ":" data_source_expression ")" full_edge_sensitive_path_description ::= "(" [ edge_identifier ] list_of_path_inputs "*>" list_of_path_outputs [ polarity_operator ] ":" data_source_expression ")" The difference is that the closing ")" was removed in each rule. In the 1364-1995 syntax there is one opening "(" and two closing ")", so they are not balanced. In 1364-2001 they are now balanced. Does 1364-2001 indicate the proper syntax? Perhaps not. Verilog-XL, NC-Verilog, and MTI all seem to want to parse the following third syntax for edge sensitive module path descriptions: parallel_edge_sensitive_path_description ::= "(" [ edge_identifier ] specify_input_terminal_descriptor "=>" "(" specify_output_terminal_descriptor [ polarity_operator ] ":" data_source_expression ")" ")" full_edge_sensitive_path_description ::= "(" [ edge_identifier ] list_of_path_inputs "*>" "(" list_of_path_outputs [ polarity_operator ] ":" data_source_expression ")" ")" The difference between the 1364-1995 syntax and the above is the *addition* of a second opening "(" before the outputs. Here is a concrete example showing each of the above three syntaxes. specify ( posedge in => out : data ) ) = 1; // 1364-1995 syntax ( posedge in => out : data ) = 1; // 1364-2001 syntax ( posedge in => ( out : data ) ) = 1; // syntax required by Verilog-XL, NC-Verilog and MTI endspecify Dennis Marsa Xilinx, Inc. |
| Fix |
In Syntax 14-4 and in A.7.4, the syntax of parallel_edge_sensitive_path_description and full_edge_sensitive_path_description should be corrected as follows:
CHANGE
parallel_edge_sensitive_path_description ::=
"(" [ edge_identifier ] specify_input_terminal_descriptor "=>"
specify_output_terminal_descriptor [ polarity_operator ] ":" data_source_expression ")"
TO
parallel_edge_sensitive_path_description ::=
"(" [ edge_identifier ] specify_input_terminal_descriptor "=>"
"(" specify_output_terminal_descriptor [ polarity_operator ] ":" data_source_expression ")" ")"
and
CHANGE
full_edge_sensitive_path_description ::=
"(" [ edge_identifier ] list_of_path_inputs "*>"
list_of_path_outputs [ polarity_operator ] ":" data_source_expression ")"
TO
full_edge_sensitive_path_description ::=
"(" [ edge_identifier ] list_of_path_inputs "*>"
"(" list_of_path_outputs [ polarity_operator ] ":" data_source_expression ")" ")"
The quotation marks around a symbol in the above mean it should be in bold font. In both cases, the correction is an extra pair of parentheses around the outputs. |
| Audit-Trail |
From: Shalom Bresticker <Shalom.Bresticker@motorola.com> To: Dennis Marsa <drm@xilinx.com> Cc: etf-bugs@boyd.com Subject: Re: errata/338: syntax of edge sensitive module path descriptions Date: Thu, 01 May 2003 17:48:26 +0300 It seems to me that your third syntax always was and is the correct syntax. If you look at the examples on the page following the syntax boxes you reference, in both 1995 and 2001, you will find the extra left parenthesis there. You will also find the error pointed out way back in http://boydtechinc.com/btf/archive/btf_1997/1210.html . I don't know how and why a right parenthesis was deleted instead. |
| Unformatted |
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